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| United States Patent |
6,054,902
|
|
Masato
|
April 25, 2000
|
High-frequency amplifier
Abstract
A high-frequency amplifier that can reduce the size, weight and price of a
device that contains this high-frequency amplifier. The high-frequency
amplifier has, for example, an input matching circuit of the low-pass type
and an input matching circuit of the high-pass type, connected in parallel
and provided at the input side or terminal of a power amplification
circuit. Matching is thereby performed corresponding to either one of two
kinds of transmission input signals, whose frequencies are different from
each other, by the input matching circuit of the low-pass type, and by the
input matching circuit of the high-pass type, respectively. Moreover, for
example, an output matching circuit of the low-pass type and an output
matching circuit of the high-pass type are connected in parallel and
provided at the output side or terminal of the power amplification
circuit. Matching is performed corresponding to either one of two
transmission output signal frequencies by the output matching circuit of
the low-pass type, and the output matching circuit of the high-pass type,
respectively.
| Inventors:
|
Masato; Yoshihito (Machida, JP)
|
| Assignee:
|
Murata Maufacturing Co., Ltd. (JP)
|
| Appl. No.:
|
909211 |
| Filed:
|
August 11, 1997 |
Foreign Application Priority Data
| Current U.S. Class: |
330/306; 330/147; 330/148 |
| Intern'l Class: |
H03F 003/191 |
| Field of Search: |
330/306,302,286,147,148,303
|
References Cited
U.S. Patent Documents
| 4107621 | Aug., 1978 | Furutani et al. | 330/306.
|
| 4803443 | Feb., 1989 | Takagi et al. | 330/286.
|
| 5420541 | May., 1995 | Upton et al. | 330/286.
|
| Foreign Patent Documents |
| 404047701 | Feb., 1992 | JP | 330/302.
|
Primary Examiner: Lee; Benny
Assistant Examiner: Nguyen; Khanh Van
Attorney, Agent or Firm: Ostrelenk, Faber, Gerb & Soffen, LLP
Claims
What is claimed is:
1. A high-frequency amplifier comprising:
an input matching circuit which is operable for performing matching
corresponding to both a first high-frequency input signal and to a second
high-frequency input signal, whose frequency is different from that of the
first high-frequency input signal;
an amplification circuit, which is connected to an output of the input
matching circuit, and which is operable for outputting a first
high-frequency output signal by amplifying the first high-frequency input
signal, and for outputting a second high-frequency output signal by
amplifying the second high-frequency input signal;
a first output terminal;
a first output matching circuit, which is connected to an output of said
amplification circuit, which is operable for performing matching
corresponding to the first high-frequency output signal and outputting
said first high-frequency output signal to said first output terminal;
a second output terminal; and
a second output matching circuit, which is connected lo the output of said
amplification circuit in parallel with said first output matching circuit,
for performing matching corresponding to the second high-frequency output
signal and outputting said second high-frequency output signal to said
second output terminal;
wherein said first and second output terminals are electrically separated
from each other for respectively outputting said first and second output
signals from said high-frequency amplifier.
2. The high-frequency amplifier according to claim 1, wherein said input
matching circuit comprises a low-pass filter.
3. The high-frequency amplifier according to claim 1, wherein said first
and second output matching circuits comprise respective filters.
4. The high-frequency amplifier according to claim 3, wherein said first
output matching circuit comprises a low-pass filter and said second output
matching circuit comprises a high-pass filter.
5. The high-frequency amplifier according to claim 4, wherein said input
matching circuit comprises a low-pass filter.
6. The high-frequency amplifier according to claim 3, wherein said first
and second output matching circuits comprise respective low-pass filters.
7. The high-frequency amplifier according to claim 6, wherein said input
matching circuit comprises a low-pass filter.
8. The high-frequency amplifier according to claim 3, wherein said
respective filters have overlapping pass ranges.
9. The high-frequency amplifier according to claim 3, wherein said
respective filters have non-overlapping pass ranges.
10. A high-frequency amplifier comprising:
a first input terminal;
a first input matching circuit which is operable for performing matching
corresponding to a first high-frequency input signal received from said
first input terminal;
a second input terminal;
a second input matching circuit, which is operable for performing matching
corresponding to a second high-frequency input signal received from said
second input terminal whose frequency is different from that of the first
high-frequency input signal;
wherein said first and second input terminals are electrically separated
from each other for respectively receiving said first and second input
signals to said high-frequency amplifier;
an amplification circuit, which is connected to an output of each of the
input matching circuits, which is operable for outputting a first
high-frequency output signal by amplifying the first high-frequency input
signal, and for outputting a second high-frequency output signal by
amplifying the second high-frequency input signal;
a first output matching circuit, which is connected to an output of said
amplification circuit, and which is operable for performing matching and
thereby outputting the first high-frequency output signal to a first
output terminal; and
a second output matching circuit, which is connected to the output of said
amplification circuit, and which is operable for performing matching and
thereby outputting the second high-frequency output signal to a second
output terminal;
wherein said first and second output terminals are electrically separated
from each other for respectively outputting said first and second output
signals from said high-frequency amplifier.
11. A high-frequency amplifier comprising:
a first input matching circuit which is operable for performing matching
corresponding to a first high-frequency input signal;
a second input matching circuit, which is connected in parallel with said
first input matching circuit, and which is operable for performing
matching corresponding to a second high-frequency input signal, whose
frequency is different from that of the first high-frequency input signal;
an amplification circuit, which is connected to an output of each of the
input matching circuits, which is operable for outputting a first
high-frequency output signal by amplifying the first high-frequency input
signal, and for outputting a second high-frequency output signal by
amplifying the second high-frequency input signal;
a first output matching circuit, which is connected to an output of said
amplification circuit, and which is operable for performing matching
corresponding to the first high-frequency output signal; and
a second output matching circuit, which is connected to the output of said
amplification circuit in parallel with said first output matching circuit,
and which is operable for performing matching corresponding to the second
high-frequency output signal;
wherein said first input matching circuit is a low-pass filter matching
circuit which cuts off the second high-frequency input signal, whose
frequency is higher than that of said first high-frequency input signal,
and wherein said second input matching circuit is a high-pass filter
matching circuit which cuts off the first high-frequency input signal.
12. The high-frequency amplifier according to claim 11, wherein said first
output matching circuit is a low-pass filter matching circuit which cuts
off the second high-frequency input signal, whose frequency is higher than
that of said first high-frequency output signal, and wherein said second
output matching circuit is a high-pass filter matching circuit which cuts
off the first high-frequency output signal.
13. A high-frequency amplifier comprising:
a first input matching circuit which is operable for performing matching
corresponding to a first high-frequency input signal;
a second input matching circuit, which is connected in parallel with said
first input matching circuit, and which is operable for performing
matching corresponding to a second high-frequency input signal, whose
frequency is different from that of the first high-frequency input signal;
an amplification circuit, which is connected to an output of each of the
input matching circuits, which is operable for outputting a first
high-frequency output signal by amplifying the first high-frequency input
signal, and for outputting a second high-frequency output signal by
amplifying the second high-frequency input signal;
a first output matching circuit, which is connected to an output of said
amplification circuit, and which is operable for performing matching
corresponding to the first high-frequency output signal; and
a second output matching circuit, which is connected to the output of said
amplification circuit in parallel with said first output matching circuit,
and which is operable for performing matching corresponding to the second
high-frequency output signal;
wherein said first output matching circuit is a low-pass filter matching
circuit which cuts off the second high-frequency input signal, whose
frequency is higher than that of said first high-frequency output signal,
and wherein said second output matching circuit is a high-pass filter
matching circuit which cuts off the first high-frequency output signal.
14. A high-frequency amplifier comprising:
a first input matching circuit which is operable for performing matching
corresponding to a first high-frequency input signal;
a second input matching circuit, which is connected in series to an output
of said first input matching circuit, and which is operable for performing
matching corresponding to a second high-frequency input signal, whose
frequency is different from that of the first high-frequency input signal;
an amplification circuit, which is connected to an output of said second
input matching circuit, and which is operable for outputting a first
high-frequency output signal by amplifying the first high-frequency input
signal, and for outputting a second high-frequency output signal by
amplifying the second high-frequency input signal;
a first output matching circuit, which is connected to an output of said
amplification circuit, and which is operable for performing matching
corresponding to the first high-frequency output signal; and
a second output matching circuit, which is connected to the output of said
amplification circuit in parallel with said first output matching circuit,
and which is operable for performing matching corresponding to the second
high-frequency output signal.
15. The high-frequency amplifier according to claim 14, wherein said first
input matching circuit is a high-pass filter matching circuit that permits
the second high-frequency input signal, whose frequency is higher than
that of said first high-frequency input signal, to pass therethrough, and
wherein said second input matching circuit is a low-pass filter matching
circuit that permits the first high-frequency input signal to pass
therethrough.
16. The high-frequency amplifier according to claim 14, wherein said first
input matching circuit is a low-pass filter matching circuit that permits
the second high-frequency input signal, whose frequency is lower than that
of said first high-frequency input signal, to pass therethrough, and
wherein said second input matching circuit is a high-pass filter matching
circuit that permits the first high-frequency input signal to pass
therethrough.
17. The high-frequency amplifier according to claim 14, wherein said first
and second input matching circuits comprise respective filters.
18. The high-frequency amplifier according to claim 17, wherein said
respective filters have overlapping pass ranges.
19. The high-frequency amplifier according to claim 18, wherein said
respective filters are low-pass filters.
20. The high-frequency amplifier according to claim 18, wherein said
respective filters are high-pass filters.
21. The high-frequency amplifier according to any one of claims 14, 15, 16,
19 and 20, wherein said first output matching circuit is a low-pass filter
matching circuit that cuts off the second high-frequency input signal,
whose frequency is higher than said first high-frequency output signal,
and wherein said second output matching circuit is a high-pass filter
matching circuit that cuts off the first high-frequency output signal.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a high-frequency amplifier
suitable for use in radio communication equipment such as portable
telephones and cordless telephones and, more particularly, to a
high-frequency amplifier which performs matching corresponding to each of
a plurality of high-frequency signals of different frequencies and that
these high-frequency signals are amplified by a single amplification
circuit.
2. Description of the Related Art
Hitherto, in mobile (radio) communication equipment such as portable
telephones and cordless telephones, radio waves of a corresponding
dedicated frequency band (namely, an exclusive or private frequency band)
have been used. Therefore, only a high-frequency amplifier for amplifying
high-frequency radio signals in the exclusive frequency band is needed to
be provided in a transmitting device (or transmitter) incorporated in a
portable telephone or the like.
Hereinafter, a conventional high-frequency amplifier will be described with
reference to FIG. 10.
In FIG. 10, reference numeral 1 designates the conventional high-frequency
amplifier. This high-frequency amplifier 1 is provided in a transmitter
incorporated in, for example, a portable telephone set and is a power
amplifier dedicated to amplifying high-frequency signals in a dedicated
frequency band, which are transmitted as radio waves from this portable
telephone. For instance, the frequencies of the dedicated frequency band
range from 890 MHz to 915 MHz, the center frequency thereof using 902.5
MHz, and the high-frequency amplifier 1 may be suitable for amplifying
only high-frequency signals of such a frequency band.
Reference numeral 2 denotes an input terminal of the high-frequency
amplifier 1. This input terminal 2 is connected to a transmission signal
generating circuit (not shown) incorporated in the portable telephone,
which synthesizes a signal from a speech signal and a carrier signal and
outputs transmission input signals (namely, high-frequency input signals),
to this input terminal 2.
Reference numeral 3 designates an input matching circuit connected to the
input terminal 2 through a coupling capacitor 4. This input matching
circuit 3 is configured by connecting a coil 5, which serves as an
inductive device or element, to a capacitor 6, which serves as a
capacitive device or element, in an L-shaped configuration, as illustrated
in FIG. 10. Parameters such as the inductance of the coil 5 and the
capacitance of the capacitor 6 are set in such a manner that matching is
achieved corresponding to the center frequency (namely, 902.5 MHz) of the
transmission input signal. Namely, a reflection coefficient corresponding
to the center frequency of the transmission input signal is optimized.
Moreover, the parameters of the coil 5 and the capacitor 6 are set in such
a way that the input return loss of the high-frequency amplifier 1 is
minimized.
Reference numeral 7 designates a power amplification circuit connected to
the output terminal of the input matching circuit 3. This power
amplification circuit 7 comprises a field effect transistor (hereunder
referred to as "FET") 8, which is operative to perform power
amplification, and a bias circuit (not shown). Further, the power
amplification circuit 7 amplifies the transmission input signal enough so
that the input signal can be transmitted by the portable telephone, for
example, to 1 W or so. The amplified transmission output signals are
outputted to an output matching circuit 9 (to be described later).
Reference numeral 9 denotes the output matching circuit provided at an
output side of the power amplification circuit 7. This output matching
circuit 9 is constituted by connecting a coil 10 to a capacitor 11 in an
L-shaped configuration, almost the same as the input matching circuit 3.
Parameters such as the inductance of the coil 10 and the capacitance of
the capacitor 11 are set in such a manner that matching is achieved
corresponding to the center frequency (namely, 902.5 MHz) of the
transmission output signal. Namely, by taking the output characteristics,
the bias conditions and gain of the power amplification circuit 7 into
consideration, each of the parameters of the coil 10 and the capacitor 11
is set in such a way that the reflection coefficient corresponds to the
center frequency of the aforementioned transmission output signal.
Reference numeral 12 designates a coupling capacitor for eliminating a bias
current. Reference numeral 13 denotes an output terminal of the
high-frequency amplifier 1. This output terminal 13 is connected to an
antenna attached to the portable telephone.
In the conventional high-frequency amplifier 1 configured in this manner,
the input matching circuit 3 is set in such way that the matching
corresponds to the transmission input signal, whose center frequency is
902.5 MHz.
However, in some cases, the transmission frequency band of a portable
telephone must vary with the area, in which the portable telephone is
used. For example, the frequency band may range from 890 MHz to 915 MHz in
a certain area, and may range from 1430 MHz to 1450 MHz in another area.
Thus, a portable telephone of the common type, by which calls can be made
in a plurality of areas, must be able to transmit in at least two
different frequency bands.
Thus, as shown in FIG. 11, another portable telephone of the common type
has a parallel connection of a first high-frequency amplifier 21, by which
matching is accomplished corresponding to the frequency band of a certain
area, and a second high-frequency amplifier 22, by which matching is
accomplished corresponding to the frequency band used in another area.
Changeover switches 23 are provided at the input side or terminal and the
output side or terminal of each of the high-frequency amplifiers 21 and 22
so as to amplify transmission signals in two different frequency bands.
This amplifier, however, is required to have two power amplification
circuits 21 and 22, of the same configuration, in parallel, as well as the
changeover switches 23. Consequently, the size of a circuit board, on
which these circuits and switches are mounted, increases. Moreover, it is
difficult to reduce the size and weight of the amplifier. Additionally,
the number of parts or components increases. This results in an increase
in the cost of the amplifier.
SUMMARY OF THE INVENTION
The present invention avoids the aforementioned problems of the
conventional high-frequency amplifier.
The present invention provides a high-frequency amplifier which can amplify
high-frequency signals having two different frequencies, to thereby reduce
the size, weight and price of a device in which this high-frequency
amplifier is provided.
To achieve the foregoing object, in accordance with a first aspect of the
present invention, there is provided a high-frequency amplifier that
comprises: an input matching circuit for performing a matching
corresponding to a first high-frequency input signal and to a second
high-frequency input signal having different frequencies; an amplification
circuit, which is connected to an output side or terminal of the input
matching circuit, for outputting a first high-frequency output signal by
amplifying the first high-frequency input signal, and alternatively, for
outputting a second high-frequency output signal by amplifying the second
high-frequency input signal; a first output matching circuit, which is
connected to an output side or terminal of the aforesaid amplification
circuit, for performing a matching corresponding to the first
high-frequency output signal; and a second output matching circuit, which
is connected to the output side or terminal of the amplification circuit
in parallel with the first output matching circuit, for performing a
matching corresponding to the second high-frequency output signal.
Thus, by connecting the first and second output matching circuits in
parallel with each other as above described, matching corresponding to
each of the first and second high-frequency output signals can be
effected. This is done by setting optimum reflection coefficients, which
respectively correspond to the first and second high-frequency output
signals, by taking the output characteristics, bias conditions and gain of
the amplification circuit into consideration.
Thus, the first output matching circuit sets an optimum reflection
coefficient corresponding to the first high-frequency output signal, while
the second output matching circuit sets an optimum reflection coefficient
corresponding to the second high-frequency output signal. By connecting
the output matching circuits in parallel with each other, matching
corresponding to each of the high-frequency signals is achieved by a
single high-frequency amplifier.
On the other hand, matching corresponding to both the first and second
high-frequency input signals is effected by the input matching circuit.
Namely, matching corresponding to each of the first and second
high-frequency input signals is accomplished in such a way that the input
return loss of this high-frequency amplifier decreases.
Note that the input matching circuit according to the above-described first
aspect of the present invention may be constituted by either a single
circuit or by a combination of a plurality of input matching devices.
Thus, in accordance with a second aspect of the present invention, there
is provided a high-frequency amplifier that comprises: a first input
matching circuit for performing matching corresponding to a first
high-frequency input signal; and a second input matching circuit, which is
connected in parallel with the first input matching circuit, for
performing matching corresponding to a second high-frequency input signal,
whose frequency is different from that of the first high-frequency input
signal.
Thus, by connecting the first and second input matching circuits in
parallel with each other as described hereinabove, matching corresponding
to each of the first and second high-frequency input signals can be
accurately or suitably effected.
Since the first and second high-frequency input signals are different in
frequency from each other, to achieve matching corresponding to each of
the high-frequency input signals in such a manner as to minimize the input
return loss, it is preferable for a reflection coefficient corresponding
to the first high-frequency input signal and another reflection
coefficient corresponding to the second high-frequency input signal to be
set at optimum values, by the first and second input matching circuits,
respectively.
By connecting the input matching circuits in parallel with each other,
matching is accurately or appropriately achieved corresponding to each of
the two high-frequency input signals, whose frequencies are different from
each other, as in the case of the first aspect of the present invention.
According to a third aspect of the invention, the first input matching
circuit comprises a low-pass filter that performs matching corresponding
to the first high-frequency input signal and cuts off the second
high-frequency input signal, whose frequency is higher than that of the
first high-frequency input signal. Moreover, the second input matching
circuit is a high-pass filter that performs matching corresponding to the
second high-frequency input signal and cuts off the first high-frequency
input signal.
In such a configuration, a matching circuit of the low-pass filter type is
employed as the first input (matching) circuit. Thus, the first input
matching circuit has frequency characteristics similar to those of a
low-pass filter, namely, the property of cutting off the second
high-frequency input signal, whose frequency is higher than that of the
first high-frequency input signal. Therefore, even if the parameters
corresponding to the circuit elements composing the first input matching
circuit (for instance, the inductance of the coil and the capacitance of
the capacitor) are changed so as to perform matching corresponding to the
first high-frequency input signal, and if the reflection coefficient
corresponding to the first high-frequency input signal is thus adjusted,
the reflection coefficient corresponding to the second high-frequency
input signal, which is set by the second input matching circuit, hardly
changes.
Further, a matching circuit of the high-pass filter type is employed as the
second input (matching) circuit. Thus, the second input matching circuit
has frequency characteristics similar to those of a high-pass filter,
namely, the property of cutting off the first high-frequency input signal,
whose frequency is lower than that of the second high-frequency input
signal. Therefore, even if the parameters corresponding to the circuit
elements composing the second input matching circuit (for instance, the
inductance of the coil and the capacitance of the capacitor) are changed
so as to perform matching corresponding to the second high-frequency input
signal, and if the reflection coefficient corresponding to the second
high-frequency input signal is thus adjusted, the reflection coefficient
corresponding to the first high-frequency input signal, which is set by
the first input matching circuit, scarcely changes.
Thus, the first and second input matching circuits are independent from
each other. Hence, the setting of the reflection coefficients by the first
input matching circuit and by the second input matching circuit are
achieved independently of each other. Consequently, matching is easily
accomplished corresponding to two high-frequency input signals with
different frequencies.
In accordance with a fourth aspect of the present invention, there is
provided still another high-frequency amplifier that comprises: a first
input matching circuit for performing matching corresponding to a first
high-frequency input signal; and a second input matching circuit, which is
connected in series to an output side or terminal of the first input
matching circuit, for performing matching corresponding to a second
high-frequency input signal, whose frequency is different from that of the
first high-frequency input signal.
By connecting the first and second input matching circuits in series with
each other, matching corresponding to each of the first and second
high-frequency input signals can be accurately or suitably effected.
Since the first and second high-frequency input signals are different in
frequency from each other, to achieve matching corresponding to each of
the high-frequency input signals in such a manner as to minimize the input
return loss, it is important to set a reflection coefficient corresponding
to the first high-frequency input signal and to set another reflection
coefficient corresponding to the second high-frequency input signal at
optimum values, respectively.
Thus, the first input matching circuit sets the reflection coefficient,
which corresponds to the first high-frequency input signal, at an optimum
value, while the second input matching circuits sets the reflection
coefficient, which corresponds to the second high-frequency input signal,
at an optimum value. Further, by connecting the input matching circuits in
series with each other, matching is accurately or appropriately achieved
corresponding to both of the two high-frequency input signals, whose
frequencies are different from each other.
On the other hand, by connecting the first and second output matching
circuits in parallel with each other, matching can be effected
corresponding to both of the first and second high-frequency output
signals, as in the case of the first aspect of the present invention.
In a fifth aspect of the present invention, the first input matching
circuit according to the fourth aspect of the invention is a matching
circuit of the high-pass filter type that performs matching corresponding
to the first high-frequency input signal and permits the second
high-frequency input signal, whose frequency is higher than that of the
first high-frequency input signal, to pass therethrough. Moreover, the
second input matching circuit is a matching circuit of the low-pass filter
type that performs matching corresponding to the second high-frequency
input signal and permits the first high-frequency input signal to pass
therethrough.
As with the previous aspects of the invention, the first and second input
matching circuits are independent of each other. Therefore, the setting of
the reflection coefficient by the first input matching circuit and the
setting of the reflection coefficient by the second input matching circuit
are achieved independently of each other. Consequently, matching is more
easily accomplished corresponding to each of the two kinds of the
high-frequency input signals, whose frequencies are different from each
other.
Furthermore, in the case of a sixth aspect of the invention, which is a
modification of the fourth aspect of the present invention, the first
input matching circuit is a matching circuit of the low-pass filter type
that performs matching corresponding to the first high-frequency input
signal and permits the second high-frequency input signal, whose frequency
is lower than that of the first high-frequency input signal, to pass
therethrough. Further, the second input matching circuit is a matching
circuit of the high-pass filter type that performs matching corresponding
to the second high-frequency input signal and permits the first
high-frequency input signal to pass therethrough. Advantages or effects
similar to those of the fifth aspect of the present invention are
obtained.
In the case of a seventh aspect of the invention, which is a feature of any
one of the first, second, third, fourth, fifth or sixth aspects of the
present invention, the first output matching circuit is a matching circuit
of the low-pass filter type that performs matching corresponding to the
first high-frequency output signal and cuts off the second high-frequency
output signal, whose frequency is higher than that of the first
high-frequency output signal. Moreover, the second output matching circuit
is a matching circuit of the high-pass filter type that performs matching
corresponding to the second high-frequency output signal and cuts off the
first high-frequency output signal.
In the case of such a configuration, a matching circuit of the low-pass
filter type is employed as the first output (matching) circuit. Thus, the
first output matching circuit has frequency characteristics similar to
those of a low-pass filter, namely, the property of cutting off the second
high-frequency output signal, whose frequency is higher than that of the
first high-frequency output signal. Therefore, even if the parameters
corresponding to the circuit elements composing the first input matching
circuit (for instance, the inductance of the coil and the capacitance of
the capacitor) are changed so as to perform matching corresponding to the
first high-frequency output signal, and if the reflection coefficient
corresponding to the first high-frequency output signal is thus regulated,
the reflection coefficient corresponding to the second high-frequency
output signal, which is set by the second output matching circuit, hardly
changes.
Further, a matching circuit of the high-pass filter type is employed as the
second output (matching) circuit. Thus, the second input matching circuit
has frequency characteristics similar to those of a high-pass filter,
namely, the property of cutting off the first high-frequency output
signal, whose frequency is lower than that of the second high-frequency
output signal. Therefore, even if the parameters corresponding to the
circuit elements composing the second output matching circuit (for
instance, the inductance of the coil and the capacitance of the capacitor)
are changed so as to perform matching corresponding to the second
high-frequency output signal, and if the reflection coefficient
corresponding to the second high-frequency output signal is thus
regulated, the reflection coefficient corresponding to the first
high-frequency output signal, which is set by the first output matching
circuit, scarcely changes.
Thus, the first and second output matching circuits are independent of each
other. Hence, the setting of the reflection coefficient by the first
output matching circuit and the setting of the reflection coefficient by
the second output matching circuit are achieved independently of each
other. Consequently, matching is easily accomplished corresponding to each
of the two kinds of high-frequency output signals, whose frequencies are
different from each other.
According to the first aspect of the invention, since the first and second
output matching circuits are connected to the output side or terminal of
the amplifying circuit in parallel with each other, the amplification
factor corresponding to each of the high-frequency output signals can be
maximized. Thereby, the two kinds of high-frequency output signals, whose
frequencies are different from each other, can be amplified by a single
high-frequency amplifier.
Therefore, the high-frequency amplifier of the present invention does not
require changeover switches and two amplification circuits of similar
configurations, which are required in the conventional amplifier.
Consequently, the size, weight and price of a device, in which the
high-frequency amplifier is provided, can be reduced.
In the case of the second aspect of the present invention, the first and
second input matching circuits are connected in parallel with each other
at the input side of the amplification circuit, while the first and second
output matching circuits are connected in parallel with each other at the
output side of the amplification circuit. Thus, matching can be performed
corresponding to each of the two kinds of high-frequency input signals,
whose frequencies are different from each other, at the input side of the
amplification circuit. Thus, the input return loss corresponding to each
of the high-frequency signals can be minimized. Moreover, the
amplification factor corresponding to each of the high-frequency signals
can be maximized.
In the case of the third aspect of the present invention, a matching
circuit of the low-pass filter type is employed as the aforesaid first
input matching circuit. Moreover, the matching circuit of the high-pass
filter type, which performs a matching correspondingly to the second
high-frequency input signal and cuts off the first high-frequency input
signal, is employed as the aforesaid second input matching circuit. Thus,
even if the parameters corresponding to the circuit elements composing the
first input matching circuit are changed so as to perform matching
corresponding to the first high-frequency input signal, this can have
little effect on the matching corresponding to the first high-frequency
input signal.
Thus, the design and regulation of the first input matching circuit can be
performed independently of the second input matching circuit. Thereby, the
design and regulation of each of the input matching circuits can be
facilitated.
In the case of the fourth aspect of the present invention, the first and
second input matching circuits are connected in series with each other at
the input side of the amplification circuit, while the first and second
output matching circuits are connected in parallel with each other at the
output side of the amplification circuit. Thus, matching can be performed
corresponding to each of the two kinds of high-frequency input signals,
whose frequencies are different from each other, at the input side of the
amplification circuit. Thus, the input return loss corresponding to each
of the high-frequency signals can be minimized.
In the case of the fifth aspect of the present invention, matching circuits
of the low-pass filter type are employed as both the aforesaid first and
second input matching circuits. Thus, even if the parameters corresponding
to the circuit elements composing the second input matching circuit are
changed so as to perform matching corresponding to the second
high-frequency input signal, this can have little effect on the matching
corresponding to the second high-frequency input signal.
Thus, the design and regulation of the first input matching circuit can be
performed independently of the second input matching circuit. Thereby, the
design and regulation of each of the input matching circuits can be
further facilitated.
Further, in the case where the first input matching circuit is a matching
circuit of the low-pass filter type and where the aforesaid second input
matching circuit is a matching circuit of the high-pass filter type,
advantages or effects similar to those of the fifth aspect of the present
invention are obtained.
In the case of the seventh high-frequency amplifier of the present
invention, a matching circuit of the low-pass filter type is employed as
the first output matching circuit, and a matching circuit of the high-pass
filter type is employed as the aforesaid second output matching circuit.
Thus, even if the parameters corresponding to the circuit elements
composing the first output matching circuit are changed so as to perform
matching corresponding to the first high-frequency output signal, this can
have little effect on the matching corresponding to the second
high-frequency output signal. Further, even if the parameters
corresponding to the circuit elements composing the second output matching
circuit are changed so as to perform matching corresponding to the second
high-frequency output signal, this can have little effect on the matching
corresponding to the first high-frequency output signal.
Thus, the design and regulation of the first output matching circuit can be
performed independently of those of the second output matching circuit.
Thereby, the design and regulation of each of the output matching circuit
can be facilitated.
BRIEF DESCRIPTION OF THE DRAWINGS
Other features, objects and advantages of the present invention will become
apparent from the following description of embodiments of the invention
with reference to the drawings in which like reference characters
designate like or corresponding parts throughout several views, and in
which:
FIG. 1 is a circuit diagram illustrating the configuration of a first
embodiment of the present invention;
FIG. 2 is a characteristic diagram illustrating the frequency
characteristics of an output matching circuit of the low-pass type and
another output matching circuit of the high-pass type, which are provided
in the first embodiment of the present invention;
FIG. 3 is a circuit diagram illustrating the configuration of a second
embodiment of the present invention;
FIG. 4 is a circuit diagram illustrating the configuration of a third
embodiment of the present invention;
FIG. 5 is a circuit diagram illustrating the configuration of a fourth
embodiment of the present invention;
FIG. 6 is a characteristic diagram illustrating the frequency
characteristics of an output matching circuit of the low-pass type and
another output matching circuit of the high-pass type, which are provided
in the fourth embodiment of the present invention;
FIG. 7 is a characteristic diagram illustrating the input return loss
characteristics of the fourth embodiment of the present invention;
FIG. 8 is a circuit diagram illustrating the configuration of a fifth
embodiment of the present invention;
FIG. 9 is a circuit diagram illustrating the configuration of a sixth
embodiment of the present invention;
FIG. 10 is a circuit diagram illustrating the configuration of a
conventional high-frequency amplifier;
FIG. 11 is a block circuit diagram illustrating the configuration of
another conventional high-frequency amplifier having changeover switches;
and
FIG. 12 is a circuit diagram illustrating a modification of the fourth
embodiment of the invention.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in
detail by referring to the accompanying drawings.
First, an example of application of a high-frequency amplifier embodying
the present invention, namely, a first embodiment of the present invention
to a high-frequency amplifier for amplifying a transmission signal of a
portable telephone of the common type will be cited as an example, and
will be described by referring to FIGS. 1 and 2.
In FIG. 1, reference numeral 31 designates a high-frequency amplifier of
the present invention. This high-frequency amplifier 31 is, for example, a
high-frequency power amplifier provided in a portable telephone adapted to
send two kinds of transmission (radio) waves, the corresponding frequency
bands of which are different from each other, and is utilized to amplify
two kinds of transmission signals (namely, high-frequency signals) used as
the transmission waves of different frequency bands. For instance, in the
case that the frequencies of the frequency band of the transmission waves
to be used in a certain area range from 890 MHz to 915 MHz and the center
frequency f1 thereof is 902.5 MHz and that the frequencies of the
frequency band of the transmission waves to be used in another area range
from 1430 MHz to 1450 MHz and the center frequency f2 thereof is 1440 MHz,
this high-frequency amplifier is adjusted in such a manner as to optimally
amplify both of the transmission signal, whose center frequency is f1, and
the transmission signal, whose center frequency is f2.
Reference numeral 32 designates an input terminal of a high-frequency
amplifier 31. This input terminal 32 is connected to a transmission signal
generating circuit (not shown) of the portable telephone of the common
type. Transmission input signals, which are two kinds of high-frequency
input signals of different frequency bands, are inputted from this
transmission signal generating circuit to this input terminal 32. Namely,
a transmission input signal A1, whose center frequency is f1 (namely,
902.5 MHz) and another transmission input signal A2, whose center
frequency is f2 (namely, 1440 MHz), are inputted to this input terminal
32. Reference numeral 33 denotes a coupling capacitor for removing the
d.c. components of the transmission input signals A1 and A2 at the input
side of the high-frequency amplifier 31.
Reference numeral 34 denotes an input matching circuit of the low-pass
filter type (hereunder referred to as the "input matching circuit 34 of
the low-pass type"). This input matching circuit 34 of the low-pass type
is composed of a coil 35, provided for example at a halfway point on a
signal line extending from the input terminal 32 to the gate terminal of a
field effect transistor FET 38 (to be described later), and a capacitor 36
provided between the signal line and the ground. Namely, the input
matching circuit of the low-pass type 34 has a circuit configuration
similar to that of what is called a low-pass filter (LPF), in which the
coil 35 and the capacitor 36 are connected in an L-shaped configuration.
Further, in the input matching circuit 34 of the low-pass type, parameters
such as the inductance of the coil 35 and the capacitance of the capacitor
36 are set in such a way that a matching is performed correspondingly to
each of the transmission input signals A1 and A2. Namely, each of the
parameters respectively corresponding to the coil 35 and the capacitor 36
is set so that a reflection coefficient corresponding to the center
frequency f1 of the transmission input signal A1 and another reflection
coefficient corresponding to the center frequency f2 of the transmission
input signal A2 are optimized in such a way as to be brought into good
balance and that the input return loss is minimized.
Reference numeral 37 designates a power amplification circuit connected to
the output side or terminal of the input matching circuit 34 of the
low-pass type. This power amplification circuit 37 is roughly composed of
a field effect transistor 38 (hereunder referred to as an "FET 38"), an
input-side bias circuit 39 for setting an input-side bias voltage of this
FET 38, and an output-side bias circuit 40 for setting an output-side bias
voltage of the FET 38. Moreover, each of the bias circuits 39 and 40 is
constituted by connecting a d.c. power supply 41, a choke coil 42 and
bypass capacitor 43 together, as illustrated in FIG. 1.
Further, this power amplification circuit 37 amplifies the transmission
input signals A1 and A2, correspondingly to each of which a matching is
accomplished by the input matching circuit 34 of the low-pass type, to the
extent that these input signals can be used as transmission waves of the
portable telephone (for example, to 1 W or so). Moreover, this power
amplification circuit 37 outputs resultant signals to output matching
circuits 44 and 49 as transmission output signals B1 and B2, respectively.
Namely, this power amplification circuit 37 amplifies the transmission
input signal A1 and outputs the transmission output signal B1, whose
center frequency is f1. Furthermore, this power amplification circuit 37
amplifies the transmission input signal A2 and outputs the transmission
output signal B2, whose center frequency is f2.
Incidentally, although the FET 38 is provided in this power amplification
circuit 37 in this embodiment, another active element such as a bipolar
transistor may be applied thereto instead of the FET 38. Further, although
this power amplification circuit 37 is constituted by a single-stage
amplifier including the single FET 38, the circuit 37 may be constituted
by a multi-stage amplifier composed of a plurality of FETs or transistors.
Reference numeral 44 denotes an output matching circuit of the low-pass
filter type (hereunder referred to as the "output matching circuit of the
low-pass type 44") for performing a matching correspondingly to the
transmission output signal B1. This output matching circuit 44 of the
low-pass type comprises a coil 45, provided on a signal line extending
from the drain terminal of the FET 38 to an output terminal 48 (to be
described later), and a capacitor 46 provided between the signal line and
the ground. Namely, the output matching circuit of the low-pass type 44
has a circuit configuration similar to that of what is called a low-pass
filter (LPF), in which the coil 45 and the capacitor 46 are connected in
an L-shaped configuration.
Further, in this output matching circuit 44 of the low-pass type,
parameters such as the inductance of the coil 45 and the capacitance of
the capacitor 46 are set in such a manner that a matching is performed
correspondingly to the transmission output signal B1. Namely, each of the
parameters respectively corresponding to the coil 45 and the capacitor 46
is set in such a way that a reflection coefficient corresponding to the
center frequency f1 of the transmission output signal B1 is optimized.
Moreover, this output matching circuit 44 of the low-pass type has the
frequency characteristic indicated by a characteristic line or curve
.alpha.1 in FIG. 2. Namely, in the case that the parameters corresponding
to the coil 45 and the capacitor 46 are set in such a manner that a
matching is effected correspondingly to the center frequency f1 (namely,
902.5 MHz) of the transmission output signal B1, the output matching
circuit 44 of the low-pass type has the characteristics, by which signals,
whose frequencies are higher than the center frequency f1 of the
transmission output signal B1, of the frequency band are cut off.
Here, note that as above described, the center frequency f1 of the
transmission output signal B1 is, for example, 902.5 MHz, that the center
frequency f2 of the transmission output signal B2 is, for instance, 1440
MHz and that thus, the center frequency f2 of the transmission output
signal B2 is higher than the center frequency f1 of the transmission
output signal B1. As a result, as illustrated in FIG. 2, the center
frequency f2 of the transmission output signal B2 is in a cut-off region
in the frequency characteristics of the output matching circuit 44 of the
low-pass type. Therefore, this output matching circuit 44 of the low-pass
type performs a matching correspondingly to the transmission output signal
B1 and cuts off the transmission output signal B2.
Reference numeral 47 denotes a coupling capacitor for eliminating a bias
current. Further, reference numeral 48 denotes a first output terminal of
the high-frequency amplifier 31. This output terminal 48 is connected to
the antenna-side terminal of the portable telephone. Moreover, the
transmission output signal B1, correspondingly to which a matching is
performed by the output matching circuit 44 of the low-pass type, is
outputted from this output terminal 48.
Reference numeral 49 designates an output matching circuit 49 of the
high-pass filter type (hereunder referred to as an "output matching
circuit of the high-pass type"). This output matching circuit 49 of the
high-pass type is composed of a capacitor 50 provided on a signal line
extending from the drain terminal of the FET 38 to an output terminal 52
(to be described later) and a coil 51, provided between the signal line
and the ground. Namely, this output matching circuit 49 of the high-pass
type has a circuit configuration similar to that of what is called a
high-pass filter (HPF), in which the capacitor 50 and the coil 51 are
connected to each other in an L-shaped configuration.
Further, in this output matching circuit 49 of the high-pass type,
parameters such as the capacitance of the capacitor 50 and the inductance
of the coil 51 are set in such a manner that a matching is performed
correspondingly to the transmission output signal B2.
Furthermore, this output matching circuit 49 of the high-pass type has the
frequency characteristic indicated by a characteristic line or curve a2 in
FIG. 2. Namely, in the case that the parameters corresponding to the
capacitor 50 and the coil 51 are set in such a manner that a matching is
effected correspondingly to the center frequency f2 (namely, 1440 MHz) of
the transmission output signal B2, the output matching circuit 49 of the
high-pass type has the characteristics, by which signals, whose
frequencies are lower than the center f2 of the transmission output signal
B2, of the frequency band are cut off. As a result, as illustrated in FIG.
2, the center frequency f1 of the transmission output signal B1 is in a
cut-off region in the frequency characteristics of the output matching
circuit 49 of the high-pass type. Therefore, this output matching circuit
49 of the high-pass type performs a matching correspondingly to the
transmission output signal B2 and cuts off the transmission output signal
B1.
Reference numeral 52 denotes a second output terminal of the high-frequency
amplifier 31. This output terminal 52 is connected to the antenna-side
terminal of the portable telephone, together with the output terminal 48.
Namely, the output terminals 48 and 52 are connected to the antenna-side
terminal of the portable telephone in such a manner as to be in parallel
with each other. Moreover, the transmission output signal B2,
correspondingly to which a matching is performed by the output matching
circuit 49 of the high-pass type, is outputted from this output terminal
52.
The high-frequency amplifier 31 of this embodiment has the aforementioned
configuration. In accordance with this high-frequency amplifier 31, when
the transmission input signal A1 is outputted from the aforesaid
transmission signal generating circuit, the input matching circuit 34
effects a matching correspondingly to the transmission input signal A1.
Further, the power amplification circuit 37 amplifies this transmission
input signal A1 and outputs the transmission output signal B1. Moreover,
the output matching circuit 44 of the low-pass type effects a matching
correspondingly to this transmission output signal B1 and outputs this
transmission output signal B1 to the antenna-side terminal of the portable
telephone through the output terminal 48. Incidentally, the transmission
output signal B1 outputted from the power amplification circuit 37 is cut
off by the output matching circuit 49 of the high-pass type. Thus, the
transmission output signal B1 does not flow through the output terminal
52.
Meanwhile, when the transmission input signal A2 is outputted from the
aforesaid transmission signal generating circuit, the input matching
circuit 34 of the low-pass type performs a matching correspondingly to
this transmission input signal A2. Further, the power amplification
circuit 37 amplifies the transmission input signal A2 and outputs this
transmission output signal B2. Moreover, the output matching circuit 49 of
the high-pass type effects a matching correspondingly to this transmission
output signal B2 and outputs the aforesaid transmission signal B2 to the
antenna-side terminal of the portable telephone through the output
terminal 52. Incidentally, the transmission output signal B2 outputted
from the power amplification circuit 37 is cut off by the output matching
circuit 44 of the low-pass type. Thus, the transmission output signal B2
does not pass through the output terminal 48.
Hereinafter, it will be described how the aforesaid high-frequency
amplifier 31 performs a matching correspondingly to each of the
transmission output signals B1 and B2.
Namely, the transmission output signals B1 and B2 are different in
frequency from each other. To perform a matching correspondingly to each
of the transmission output signals B1 and B2, it is important to set a
reflection coefficient corresponding to the transmission output signal B1
and a reflection coefficient corresponding to the transmission output
signal B2 at optimum values, respectively, at the output-side terminal of
the power amplification circuit 37 by taking the output characteristics,
bias conditions and gain thereof into consideration.
Thus, in the output matching circuit 44 of the low-pass type, the parameter
corresponding to each of the coil 45 and the capacitor 46 composing the
output matching circuit 44 of the low-pass type are set in such a manner
that an optimum reflection coefficient corresponding to the transmission
output signal B1 is obtained. Further, in the output matching circuit 49
of the high-pass type, the parameters respectively corresponding to the
capacitor 50 and the coil 51 composing the output matching circuit 49 of
the high-pass type are set in such a way that an optimum reflection
coefficient corresponding to the transmission output signal B2 is
obtained.
Thereby, the matching is achieved correspondingly to each of the
transmission output signals B1 and B2 so that a maximum gain is obtained.
Further, in the case of the high-frequency amplifier 31 of this embodiment,
the output matching circuit 44 of the low-pass type, which cuts off a
high-frequency band according to the frequency characteristics thereof,
and the output matching circuit 49, which cuts off a low-frequency band
according to the frequency characteristics thereof, are connected in
parallel with each other, as illustrated in FIG. 1. Thereby, the output
matching circuit 44 of the low-pass type performs a matching
correspondingly to the transmission output signal B1 but cuts off the
transmission output signal B2. On the other hand, the output matching
circuit 49 of the high-pass type performs a matching correspondingly to
the transmission output signal B2 but cuts off the transmission output
signal B1.
As a result, when viewing a load from the drain terminal of the FET 38 of
the power amplification circuit 37 (namely, when facing the output
terminals 48 and 52), the circuit characteristics of the output matching
circuit 49 of the high-pass type can have only a small effect on the
reflection coefficient corresponding to the transmission output signal B1.
Instead, the influence of the circuit characteristics of the output
matching circuit 44 of the low-pass type upon the reflection coefficient
is predominant. On the other hand, the circuit characteristics of the
output matching circuit 44 of the low-pass type can have only a small
effect on the reflection coefficient corresponding to the transmission
output signal B1. Instead, the influence of the circuit characteristics of
the output matching circuit 49 of the high-pass type upon the reflection
coefficient is predominant.
Therefore, even if the parameters corresponding to the coil 45 and the
capacitor 46 provided in the output matching circuit 44 of the low-pass
type are changed so as to perform a matching correspondingly to the
transmission output signal B1, and if the reflection coefficient
corresponding to the transmission output signal B1 is regulated, the
reflection coefficient corresponding to the transmission output signal B2,
which is set by the output matching circuit 49 of the high-pass type,
hardly changes. Moreover, similarly as in this case, even if the
parameters corresponding to the capacitor 50 and the coil 51 provided in
the output matching circuit 49 of the high-pass type are changed so as to
perform a matching correspondingly to the transmission output signal B2,
and if the reflection coefficient corresponding to the transmission output
signal B2 is regulated, the reflection coefficient corresponding to the
transmission output signal B1, which is set by the output matching circuit
44 of the low-pass type, scarcely changes.
Thus, in the case of this embodiment, as a result of connecting the output
matching circuit 44 of the low-pass type and the output matching circuit
49 of the high-pass type in parallel with each other at the output side of
the high-frequency amplifier 31, each of the two kinds of the transmission
signals, whose frequencies are different from each other, can be amplified
by the circuit having the corresponding optimum characteristics.
Thereby, the two kinds of the transmission signals, whose frequencies are
different from each other, can be amplified by only providing the single
high-frequency amplifier of the present invention in the portable
telephone of the common type. Further, the necessity of the two
high-frequency amplifiers 21 and 22 and the changeover switches 23, which
are provided in the conventional high-frequency amplifier (see FIG. 10),
is eliminated. Consequently, the reduction in the size, weight and price
of the portable telephone (set), in which this high-frequency amplifier 31
is provided, can be achieved.
Furthermore, a combination of matching circuits of the low-pass type and
the high-pass type are employed as the output matching circuits 44 and 49.
Thereby, the output matching circuit 44 of the low-pass type and the
output matching circuit 49 of the high-pass type are independent of each
other. Thus, the setting of the reflection coefficient corresponding to
the transmission output signal B1 can be achieved independent of the
setting of the reflection coefficient corresponding to the transmission
output signal B2. Consequently, the design and regulation of each of the
output matching circuits 44 and 49 can be facilitated.
Next, the case of application of another high-frequency amplifier embodying
the present invention, namely, a second embodiment of the present
invention to a high-frequency amplifier for amplifying a transmission
signal of a portable telephone of the common type will be cited as another
example, and will be described by referring to FIG. 3.
Characteristic aspects of this high-frequency amplifier 61 of the present
invention, namely, this embodiment reside in that an output matching
circuit 62 of the low-pass type, which is constituted by a matching
circuit of the low-pass filter type, is employed as a first output
matching circuit for performing a matching corresponding to the
transmission output signal B1, whose center frequency is f1 (namely, 902.5
MHz), and that an output matching circuit 63 of the low-pass type, which
is constituted by a matching circuit of the low-pass filter type, is
employed as a second output matching circuit for performing a matching
corresponding to the transmission output signal B2, whose center frequency
is f2 (namely, 1440 MHz).
Namely, the output matching circuit 62 of the low-pass type is constituted
by connecting a coil 64 and a capacitor 65 with each other in an L-shaped
configuration, similarly as the output matching circuit 44 of the low-pass
type in the case of the aforementioned first embodiment. Thus, the output
matching circuit 62 has a circuit configuration which is similar to that
of a low-pass filter. Further, in this output matching circuit 62 of the
low-pass type, the parameters such as the inductance of the coil 64 and
the capacity of the capacitor 65 are set in such a manner that a matching
is performed correspondingly to the center frequency f1 of the
transmission output signal B1. Moreover, a coupling capacitor 66 for
eliminating a bypass current is provided at the output side of this output
matching circuit 62 of the low-pass type.
Moreover, the output matching circuit 63 of the low-pass type is
constituted by connecting a coil 67 and a capacitor 68 with each other in
an L-shaped configuration, similarly as the aforementioned output matching
circuit 62 of the low-pass type. Thus, the output matching circuit 63 has
a circuit configuration which is similar to that of a low-pass filter.
Further, in this output matching circuit 63 of the low-pass type, the
parameters such as the inductance of the coil 67 and the capacitance of
the capacitor 68 are set in such a manner that a matching is performed
correspondingly to the center frequency f2 of the transmission output
signal B2. Moreover, a coupling capacitor 69 for eliminating a bypass
current is provided at the output side of this output matching circuit 63
of the low-pass type.
The high-frequency amplifier 61 constructed as above described, namely,
this embodiment has advantages or effects that are nearly the same as
those of the high-frequency amplifier 31, namely, the first embodiment.
Incidentally, because both of the output matching circuits 62 and 63 are
of the low-pass filter type, the circuit characteristics of the output
matching circuit 62 and the output matching circuit 63 depend upon each
other. Thus, each of the parameters of the coil 64 and the capacitor 65
and each of the parameters of the coil 67 and the capacitor 68 are set by
being regulated in such a manner that the matching corresponding to the
transmission output signal B1 and the matching corresponding to the
transmission output signal B2 are simultaneously performed.
Next, the case of application of still another high-frequency amplifier
embodying the present invention, namely, a third embodiment of the present
invention to a high-frequency amplifier for amplifying a transmission
signal of a portable telephone of the common type will be cited as still
another example, and will be described by referring to FIG. 4. A
characteristic aspect of this embodiment resides in that an input matching
circuit provided at the input side of the high-frequency amplifier is
constructed by connecting a matching circuit of the low-pass filter type
and a matching circuit of the high-pass filter type with each other in
parallel. Incidentally, like reference characters designate like composing
elements of the aforementioned first embodiment. Moreover, the description
of such composing elements is omitted herein.
In FIG. 4, reference numeral 71 designates a high-frequency amplifier of
this embodiment. Reference numeral 72 denotes a first input terminal of
this high-frequency amplifier 71. This input terminal 72 is connected to a
transmission signal generating circuit (not shown) of the portable
telephone of the common type. Further, a transmission input signal A1,
whose center frequency is f1 (namely, 902.5 MHz) and another transmission
input signal A2, whose center frequency is f2 (namely, 1440 MHz), are
inputted to this input terminal 72.
Reference numeral 74 denotes an input matching circuit of the low-pass
filter type (hereunder referred to as the "input matching circuit 74 of
the low-pass type") connected to the input terminal 72 through a coupling
capacitor 73. This input matching circuit 74 of the low-pass type is
composed of a coil 75, on a signal line extending from the input terminal
72 to the gate terminal of a field effect transistor (FET) 38 (to be
described later), and a capacitor 76 provided between the signal line and
the ground. Namely, the input matching circuit 74 of the low-pass type has
a circuit configuration similar to that of what is called a low-pass
filter (LPF), in which the coil 75 and the capacitor 76 are connected in
an L-shaped configuration.
Further, in the input matching circuit 74 of the low-pass type, parameters
such as the inductance of the coil 75 and the capacitance of the capacitor
76 are set in such a way that a matching is performed correspondingly to
the center frequency f1 of the transmission input signal A1. Namely, each
of the parameters respectively corresponding to the coil 75 and the
capacitor 76 is set so that a reflection coefficient corresponding to the
center frequency f1 of the transmission input signal A1 is optimized and
that the input return loss is minimized.
Further, in this output matching circuit 74 of the low-pass type, nearly
like the case of the output matching circuit 44 of the low-pass type
described in the description of the first embodiment, the parameters
corresponding to the coil 75 and the capacitor 76 are set in such a manner
that a matching is performed correspondingly to the center frequency f1
(902.5 MHz) of the transmission input signal A1. Thereby, the input
matching circuit 74 of the low-pass type has the characteristics, by which
signals, whose frequencies are higher than the center frequency f1 of the
transmission input signal A1, of the frequency band are cut off (see the
characteristic line .alpha.1 in FIG. 2).
Here, note that as above described, the center frequency f1 of the
transmission input signal A1 is, for example, 902.5 MHz, that the center
frequency f2 of the transmission input signal A2 is, for instance, 1440
MHz and that thus, the center frequency f2 of the transmission input
signal A2 is higher than the center frequency f1 of the transmission input
signal A1. As a result, the center frequency f2 of the transmission output
signal A2 is in a cut-off region in the frequency characteristics of the
input matching circuit 74 of the low-pass type. Therefore, this input
matching circuit 74 of the low-pass type performs a matching
correspondingly to the transmission input signal A1 and cuts off the
transmission input signal A2.
Reference numeral 77 denotes a second input terminal of this high-frequency
amplifier 71. This input terminal 77 is connected to a transmission signal
generating circuit (not shown) of the portable telephone of the common
type, together with the input terminal 72. Namely, the aforesaid input
terminal 72 and the input terminal 77 are connected in parallel to the
transmission signal generating circuit of the portable telephone of the
common type. Further, the transmission input signals A1 and A2 are
inputted to this input terminal 77.
Reference numeral 78 denotes an input matching circuit of the high-pass
filter type (hereunder referred to as the "input matching circuit 78 of
the high-pass type"), which is connected to the input terminal 77 and
performs a matching corresponding to the transmission input signal A2.
This input matching circuit 78 of the high-pass type is composed of a
capacitor 79 acting as a capacitive element provided at a halfway point on
a signal line extending from the input terminal 77 to the FET 38, and a
coil 80, which acts as an inductive element provided between the signal
line and the ground. Namely, the input matching circuit 78 of the
high-pass type has a circuit configuration similar to that of what is
called a high-pass filter (HPF), in which the capacitor 79 and the coil 80
are connected in an L-shaped configuration.
Further, in this output matching circuit 78 of the low-pass type,
parameters such as the capacity of the capacitor 79 and the inductance of
the coil 75 are set in such a manner that a matching is performed
correspondingly to the center frequency f2 of the transmission input
signal A2.
Further, in this output matching circuit 78 of the high-pass type, nearly
like the case of the output matching circuit 49 of the high-pass type
described in the description of the first embodiment, parameters
corresponding to the capacitor 79 and the coil 80 are set in such a manner
that a matching is performed correspondingly to the center frequency f2
(1440 MHz) of the transmission input signal A2. Thereby, the input
matching circuit 78 of the high-pass type has the characteristics, by
which signals, whose frequencies are lower than the center frequency f2 of
the transmission input signal A2, of the frequency band are cut off (see
the characteristic line or curve a2 in FIG. 2). As a result, the center
frequency f1 of the transmission input signal A1 is in a cut-off region in
the frequency characteristics of the input matching circuit 78 of the
high-pass type. Therefore, this input matching circuit 78 of the high-pass
type performs a matching correspondingly to the transmission input signal
A2 and cuts off the transmission input signal A1.
The high-frequency amplifier 71 of this embodiment has the aforementioned
configuration. In accordance with this high-frequency amplifier 71, when
the transmission input signal A1 is outputted from the aforesaid
transmission signal generating circuit to the input terminal 72, the input
matching circuit 74 of the low-pass type effects a matching
correspondingly to the transmission input signal A1. At that time, the
transmission input signal A1 is also outputted to the input terminal 77.
This transmission input signal A1 is cut off by the input matching circuit
78 of the high-pass type. Therefore, this transmission input signal A1
does not flow into the power amplification circuit 37 through the input
matching circuit 78 of the high-pass type. Further, the power
amplification circuit 37 amplifies this transmission input signal A1,
correspondingly to which a matching is performed by the input matching
circuit 74 of the low-pass type, and outputs the transmission output
signal B1. Moreover, the output matching circuit 44 of the low-pass type
effects a matching correspondingly to this transmission output signal B1
and outputs this transmission output signal B1 to the antenna-side
terminal of the portable telephone through the output terminal 48.
Incidentally, the transmission output signal B1 outputted from the power
amplification circuit 37 is cut off by the output matching circuit 49 of
the high-pass type. Thus, the transmission output signal B1 does not flow
through the output terminal 52.
Meanwhile, when the transmission input signal A2 is outputted from the
aforesaid transmission signal generating circuit to the input terminal 77,
the input matching circuit 78 of the high-pass type performs a matching
correspondingly to this transmission input signal A2. At that time, the
transmission input signal A2 is also outputted to the input terminal 72.
This transmission input signal A2 is cut off by the input matching circuit
74 of the low-pass type. Therefore, this transmission input signal A2 does
not flow into the power amplification circuit 37 through the input
matching circuit 74 of the low-pass type. Further, the power amplification
circuit 37 amplifies the transmission input signal A2 and outputs this
transmission output signal B2. Moreover, the output matching circuit 49 of
the high-pass type effects a matching correspondingly to this transmission
output signal B2 ad outputs the aforesaid transmission signal B2 to the
antenna-side terminal of the portable telephone through the output
terminal 52. Incidentally, the transmission output signal B2 outputted
from the power amplification circuit 37 is cut off by the output matching
circuit 44 of the low-pass type. Thus, the transmission output signal B2
does not pass through the output terminal 48.
Hereinafter, it will be described how the input matching circuit 74 of the
low-pass type and the input matching circuit 78 of the high-pass type,
which are the characteristic composing elements of this embodiment,
perform a matching correspondingly to each of the transmission input
signals A1 and A2.
Namely, the transmission input signals A1 and A2 are different in frequency
from each other. To perform a matching correspondingly to each of the
transmission input signals A1 and A2, there is the necessity of setting a
reflection coefficient corresponding to the transmission input signal A1
and a reflection coefficient corresponding to the transmission input
signal A2 at optimum values, respectively, at the input-side terminal of
the power amplification circuit 37 in such a way that the input return
loss is minimized.
Thus, in the input matching circuit 74 of the low-pass type, the parameter
corresponding to each of the coil 75 and the capacitor 76 composing the
input matching circuit 74 of the low-pass type are set in such a manner
that an optimum reflection coefficient corresponding to the transmission
input signal A1 is obtained. Further, in the input matching circuit 78 of
the high-pass type, the parameters respectively corresponding to the
capacitor 79 and the coil 80 composing the input matching circuit 78 of
the high-pass type are set in such a way that an optimum reflection
coefficient corresponding to the transmission input signal A2 is obtained.
Thereby, the matching is achieved correspondingly to each of the
transmission input signals A1 and A2 so that the input return loss is
minimized.
Further, in the case of this embodiment, the input matching circuit 74 of
the low-pass type, which cuts off a high-frequency band according to the
frequency characteristics thereof, and the input matching circuit 78,
which cuts off a low-frequency band according to the frequency
characteristics thereof, are connected in parallel with each other.
Thereby, the input matching circuit 74 of the low-pass type performs a
matching correspondingly to the transmission input signal A1 but cuts off
the transmission input signal A2. On the other hand, the input matching
circuit 78 of the high-pass type performs a matching correspondingly to
the transmission input signal A2 but cuts off the transmission input
signal A1.
As a result, at the input side of the power amplification circuit 37, the
circuit characteristics of the input matching circuit 78 of the high-pass
type have a small effect on the reflection coefficient corresponding to
the transmission input signal A1. Instead, the influence of the circuit
characteristics of the input matching circuit 74 of the high-pass type
upon the reflection coefficient is predominant. On the other hand, the
circuit characteristics of the output matching circuit 74 of the high-pass
type have a small effect on the reflection coefficient corresponding to
the transmission input signal A2. Instead, the influence of the circuit
characteristics of the input matching circuit 78 of the low-pass type upon
the reflection coefficient is predominant.
Therefore, even if the parameters corresponding to the coil 75 and the
capacitor 76 provided in the input matching circuit 74 of the low-pass
type are changed so as to perform a matching correspondingly to the
transmission input signal A1, and if the reflection coefficient
corresponding to the transmission input signal A1 is regulated, the
reflection coefficient corresponding to the transmission input signal A2,
which is set by the input matching circuit 78 of the high-pass type,
hardly changes. Moreover, similarly as in this case, even if the
parameters corresponding to the capacitor 79 and the coil 80 provided in
the input matching circuit 78 of the high-pass type are changed so as to
perform a matching correspondingly to the transmission input signal A2,
and if the reflection coefficient corresponding to the transmission input
signal A2 is regulated, the reflection coefficient corresponding to the
transmission input signal A1, which is set by the input matching circuit
74 of the low-pass type, scarcely changes.
Thus, in the case of this embodiment, the input matching circuit 74 of the
low-pass type and the input matching circuit 78 of the high-pass type are
connected in parallel with each other at the input side of the
high-frequency amplifier 71. Moreover, the output matching circuit 44 of
the low-pass type and the output matching circuit 49 of the high-pass type
are connected in parallel with each other at the output side of the
high-frequency amplifier 71. Thereby, each of the two kinds of the
transmission signals, whose frequencies are different from each other, can
be amplified by the circuit having the corresponding optimum
characteristics. Namely, at the input side of the high-frequency amplifier
71, the input return loss corresponding to each of the transmission input
signals A1 and A2 can be minimized. Moreover, at the output side of the
high-frequency amplifier 71, the gain of amplification corresponding to
each of the transmission input signals B1 and B2 can be minimized.
Consequently, even in the case of the high-frequency amplifier 71 of this
embodiment, the reduction in the size, weight and price of the portable
telephone (set), in which this high-frequency amplifier 71 is provided,
can be achieved, similarly as in the case of the high-frequency amplifier
31 of the first embodiment.
Furthermore, a combination of matching circuits of the low-pass type and
the high-pass type are employed as the input matching circuits 74 and 79.
Thus, the input matching circuit 74 of the low-pass type and the input
matching circuit 78 of the high-pass type become independent of each
other. Thus, the setting of the reflection coefficient corresponding to
the transmission input signal A1 can be achieved independent of the
setting of the reflection coefficient corresponding to the transmission
input signal A2. Consequently, the design and regulation of each of the
input matching circuits 74 and 78 can be facilitated.
Furthermore, a matching is effected correspondingly to the transmission
input signal A1 by the input matching circuit 74 of the low-pass type,
while the transmission input signal A2 is cut off. Further, a matching is
performed correspondingly to the transmission input signal A2 by the input
matching circuit 78 of the high-pass type, while the transmission input
signal A1 is cut off. Thus, at the input side of the high-frequency
amplifier 71, a changeover switch for selectively making a selection
between the transmission input signals A1 and A2 becomes unnecessary.
Next, the case of application of yet another high-frequency amplifier
embodying the present invention, namely, a fourth embodiment of the
present invention to a high-frequency amplifier for amplifying a
transmission signal of a portable telephone of the common type will be
cited as yet another example, and will be described by referring to FIGS.
5 to 7. Characteristic aspect of this embodiment resides in that an input
matching circuit provided at the input side of the high-frequency
amplifier is constructed by connecting a matching circuit of the high-pass
filter type and a matching circuit of the low-pass filter type in series
with each other. Incidentally, like reference characters designate like
composing elements of the aforementioned first embodiment. Moreover, the
description of such composing elements is omitted herein.
In FIG. 5, reference numeral 81 designates a high-frequency amplifier of
this embodiment. Reference numeral 82 denotes an input terminal of this
high-frequency amplifier 81. This input terminal 82 is connected to a
transmission signal generating circuit (not shown) of the portable
telephone of the common type. Further, a transmission input signal A1,
whose center frequency is f1 (namely, 902.5 MHz) and another transmission
input signal A2, whose center frequency is f2 (namely, 1440 MHz), are
inputted to this input terminal 72.
Reference numeral 83 denotes an input matching circuit of the high-pass
filter type (hereunder referred to as the "input matching circuit 83 of
the high-pass type") connected to the input terminal 82. This input
matching circuit 83 of the high-pass type is composed of a capacitor 84,
which acts as an capacitive element provided at a halfway point on a
signal line extending from the input terminal 82 to the gate terminal of
the FET 38 (to be described later), and a coil 85 acting as an inductive
element provided between the signal line and the ground. Namely, the input
matching circuit 83 of the high-pass type has a circuit configuration
similar to that of what is called a high-pass filter, in which the
capacitor 84 and the coil 85 are connected in an L-shaped configuration.
Further, in the input matching circuit 83 of the high-pass type, parameters
such as the capacity of the capacitor 84 and the inductance of the coil 85
are set in such a way that a matching is performed correspondingly to the
center frequency f1 of the transmission input signal A1.
Further, this output matching circuit 83 of the high-pass type has
frequency characteristics as indicated by a characteristic line .beta.1 in
FIG. 6. Namely, the parameters corresponding to the coil 75 and the
capacitor 76 are set in such a manner that a matching is performed
correspondingly to the center frequency f1 (902.5 MHz) of the transmission
input signal A1. Thereby, this input matching circuit 83 of the high-pass
type has the characteristics, by which signals, whose frequencies are
higher than the center frequency f1 of the transmission input signal A1,
of the frequency band are made to pass therethrough.
Here, note that as above described, the center frequency f1 of the
transmission input signal A1 is, for example, 902.5 MHz, that the center
frequency f2 of the transmission input signal A2 is, for instance, 1440
MHz and that thus, the center frequency f2 of the transmission input
signal A2 is higher than the center frequency f1 of the transmission input
signal A1. As a result, the center frequency f2 of the transmission input
signal A2 is in a passing region in the frequency characteristics of the
input matching circuit 83 of the high-pass type, as illustrated in FIG. 6.
Therefore, this input matching circuit 83 of the high-pass type performs a
matching correspondingly to the transmission input signal A1 and permits
the transmission input signal A2 to path therethrough.
Reference numeral 86 denotes an input matching circuit of the low-pass
filter type (hereunder referred to as the "input matching circuit 86 of
the low-pass type"), which is connected in series with the output side of
the aforementioned input matching circuit 83 of the high-pass type and
performs a matching corresponding to the center frequency f2 of the
transmission input signal A2. This input matching circuit 86 of the
high-pass type is composed of a coil 87 acting as an inductive element
provided at a halfway point on a signal line extending from the input
terminal 82 to the FET 38, and a capacitive 88, which acts as a capacitive
element provided between the signal line and the ground. Namely, the input
matching circuit 86 of the low-pass type has a circuit configuration
similar to that of what is called a low-pass filter, in which the coil 87
and the capacitor 88 are connected in an L-shaped configuration.
Further, in this input matching circuit 86 of the low-pass type, parameters
such as the inductance of the coil 87 and the capacity of the capacitor 88
are set in such a manner that a matching is performed correspondingly to
the center frequency f2 of the transmission input signal A2.
Further, this input matching circuit 86 of the low-pass type has frequency
characteristics as indicated by a characteristic line .beta.2 in FIG. 6.
Namely, parameters corresponding to the coil 87 and the capacitor 88 are
set in such a manner that a matching is performed correspondingly to the
center frequency f2 (1440 MHz) of the transmission input signal A2.
Thereby, the input matching circuit 86 of the low-pass type has the
characteristics, by which signals, whose frequencies are lower than the
center frequency f2 of the transmission input signal A2, of the frequency
band are permitted to pass therethrough. As a result, the center frequency
f1 of the transmission input signal A1 is in a passing region in the
frequency characteristics of the input matching circuit 86 of the low-pass
type. Therefore, this input matching circuit 86 of the low-pass type
performs a matching correspondingly to the transmission input signal A2
and permits the transmission input signal A1 to pass therethrough.
The high-frequency amplifier 81 of this embodiment has the aforementioned
configuration. In accordance with this high-frequency amplifier 81, when
the transmission input signal A1 is outputted from the aforesaid
transmission signal generating circuit to the input terminal 82, the input
matching circuit 83 of the low-pass type effects a matching
correspondingly to the transmission input signal A1. Further, the power
amplification circuit 37 amplifies this transmission input signal A1 and
outputs the transmission output signal B1. Moreover, the output matching
circuit 44 of the low-pass type effects a matching correspondingly to this
transmission output signal B1 and outputs this transmission output signal
B1 to the antenna-side terminal of the portable telephone through the
output terminal 48.
Meanwhile, when the transmission input signal A2 is outputted from the
aforesaid transmission signal generating circuit to the input terminal 82,
the input matching circuit 86 of the low-pass type performs a matching
correspondingly to this transmission input signal A2. Further, the power
amplification circuit 37 amplifies the transmission input signal A2 and
outputs this transmission output signal B2. Moreover, the output matching
circuit 49 of the high-pass type effects a matching correspondingly to
this transmission output signal B2 ad outputs the aforesaid transmission
signal B2 to the antenna-side terminal of the portable telephone through
the output terminal 52.
Hereinafter, it will be described how the input matching circuits 83 and 86
of this high-frequency amplifier 81 perform a matching correspondingly to
each of the transmission input signals A1 and A2.
The transmission input signals A1 and A2 are different in frequency from
each other. To perform a matching correspondingly to each of the
transmission input signals A1 and A2, there is the necessity of setting a
reflection coefficient corresponding to the transmission input signal A1
and a reflection coefficient corresponding to the transmission input
signal A2 at optimum values, respectively, at the input-side terminal of
the power amplification circuit 37 in such a manner that the input return
loss is minimized.
Thus, in the input matching circuit 83 of the high-pass type, the parameter
corresponding to each of the capacitor 84 and the coil 85 composing the
input matching circuit 83 of the high-pass type are set in such a manner
that an optimum reflection coefficient corresponding to the transmission
input signal A1 is obtained. Further, in the input matching circuit 86 of
the low-pass type, the parameters respectively corresponding to the coil
87 and the capacitor 88 composing the input matching circuit 86 of the
low-pass type are set in such a way that an optimum reflection coefficient
corresponding to the transmission input signal A2 is obtained. Thereby,
the matching is achieved correspondingly to each of the transmission input
signals A1 and A2 so that the input return loss is minimized.
Further, in the case of the high-frequency amplifier 81 of this embodiment,
the input matching circuit 83 of the high-pass type having the frequency
characteristics, by which frequencies of a high-frequency band are
permitted to pass therethrough, and the input matching circuit 86 of the
low-pass type having the frequency characteristics, by which frequencies
of a low-frequency band are permitted to pass therethrough, are connected
in series with each other, as illustrated in FIG. 5. Thereby, the input
matching circuit 83 of the high-pass type performs a matching
correspondingly to the transmission input signal A1 and permits the
transmission input signal A2 to pass therethrough. Further, the input
matching circuit 86 of the low-pass type performs a matching
correspondingly to the transmission input signal A2 and permits the
transmission input signal A1 to pass therethrough. Consequently, the
circuit characteristic of the input matching circuit 83 of the high-pass
type and the circuit characteristic of the input matching circuit 86 of
the low-pass type do not depend upon each other.
Therefore, even if the parameters corresponding to the capacitor 84 and the
coil 85 provided in the input matching circuit 83 of the high-pass type
are changed so as to perform a matching correspondingly to the
transmission input signal A1, and if the reflection coefficient
corresponding to the transmission input signal A1 is regulated, the
reflection coefficient corresponding to the transmission input signal A2,
which is set by the input matching circuit 86 of the low-pass type, hardly
changes. Moreover, similarly as in this case, even if the parameters
corresponding to the coil 87 and the capacitor 88 provided in the input
matching circuit 86 of the low-pass type are changed so as to perform a
matching correspondingly to the transmission input signal A2, and if the
reflection coefficient corresponding to the transmission input signal A2
is regulated, the reflection coefficient corresponding to the transmission
input signal A1, which is set by the input matching circuit 83 of the
high-pass type, scarcely changes.
Referring now to FIG. 7, there is illustrated the manner of change in the
input-return-loss characteristics of the high-frequency amplifier 81 at
the time when the capacitance of the capacitor 88 provided in the input
matching circuit 86 of the high-frequency amplifier 81 is changed. Namely,
the characteristic line .gamma.1 of FIG. 7 indicates the input-return-loss
characteristics of the high-frequency amplification circuit 81 before the
capacitance of the aforementioned capacitor 88 is changed. The
characteristic line .gamma.2 indicates the input-return-loss
characteristics of the high-frequency amplification circuit 81 after the
capacitance of the aforementioned capacitor 88 is changed. As is seen from
this figure, in response to a change in the capacitance of the capacitor
88 provided in the input matching circuit 86 of the low pass type, the
input-return-loss characteristics in the vicinity of the center frequency
f2 of the transmission input signal A2 change as indicated by an arrow R.
However, the input-return-loss characteristics in the vicinity of the
center frequency f1 of the transmission input signal A1 do not change.
Namely, as is understood from FIG. 7, the circuit characteristics of the
input matching circuit 83 of the high-pass type has independence from the
circuit characteristics of the input matching circuit 86 of the high-pass
type.
Thus, the input matching circuit 83 of the high-pass type and the input
matching circuit 86 of the low-pass type are independent of each other.
Hence, the setting of the reflection coefficient corresponding to the
transmission input signal A1 can be achieved independent of the setting of
the reflection coefficient corresponding to the transmission input signal
A2. Consequently, the design and regulation of each of the input matching
circuits 83 and 86 can be further facilitated.
Thus, in the case of this embodiment, as a result of connecting the input
matching circuit 83 of the high-pass type and the input matching circuit
86 of the low-pass type in series with each other at the input side of the
high-frequency amplifier 81, and of further connecting the output matching
circuit 44 of the low-pass type and the output matching circuit 49 of the
high-pass type in parallel with each other at the output side of the
high-frequency amplifier 81, each of the two kinds of the transmission
signals, whose frequencies are different from each other, can be amplified
by the circuit having the corresponding optimum characteristics.
Thereby, the two kinds of the transmission signals, whose frequencies are
different from each other, can be amplified by only providing the single
high-frequency amplifier 81 of the present invention in the portable
telephone of the common type. Further, the necessity of the two
high-frequency amplifiers 21 and 22 and the changeover switches 23, which
are provided in the conventional high-frequency amplifier (see FIG. 11),
is eliminated. Consequently, the reduction in the size, weight and price
of the portable telephone (set), in which this high-frequency amplifier 81
is provided, can be achieved.
Furthermore, a combination of matching circuits of the high-pass type and
the low-pass type are employed as the input matching circuits 83 and 86.
Thereby, the input matching circuit 83 of the high-pass type and the input
matching circuit 86 of the low-pass type are independent of each other.
Thus, the setting of the reflection coefficient corresponding to the
transmission input signal A1 can be achieved independent of the setting of
the reflection coefficient corresponding to the transmission input signal
A2. Consequently, the design and regulation of each of the input matching
circuits 83 and 86 can be facilitated.
In a modification of the fourth embodiment of the invention, shown in FIG.
12, the positions of the low-pass type input matching circuit 86 and the
high-pass type input matching circuit 83 have been reversed.
Next, the case of application of a further high-frequency amplifier
embodying the present invention, namely, a fifth embodiment of the present
invention to a high-frequency amplifier for amplifying a transmission
signal of a portable telephone of the common type will be cited as a
further example, and will be described by referring to FIG. 8.
Characteristic aspects of this high-frequency amplifier 91 of the present
invention, namely, this embodiment reside in that an input matching
circuit 92 of the low-pass type, which is constituted by a matching
circuit of the low-pass filter type, is employed as a first input matching
circuit for performing a matching corresponding to the transmission input
signal A1, whose center frequency is f1 (namely, 902.5 MHz), and that an
input matching circuit 93 of the low-pass type, which is constituted by a
matching circuit of the low-pass filter type, is employed as a second
output matching circuit for performing a matching corresponding to the
transmission input signal A2, whose center frequency is f2 (namely, 1440
MHz).
Namely, the input matching circuit 92 of the low-pass type is constituted
by connecting a coil 94 and a capacitor 95 with each other in an L-shaped
configuration, similarly as the input matching circuit 86 of the low-pass
type in the case of the aforementioned first embodiment. Thus, the output
matching circuit 92 has a circuit configuration which is similar to that
of a low-pass filter. Further, in this input matching circuit 92 of the
low-pass type, the parameters such as the inductance of the coil 94 and
the capacitance of the capacitor 95 are set in such a manner that a
matching is performed correspondingly to the center frequency f1 of the
transmission input signal A1.
Moreover, the input matching circuit 93 of the low-pass type is constituted
by connecting a coil 96 and a capacitor 97 with each other in an L-shaped
configuration, similarly as the aforementioned input matching circuit 92
of the low-pass type. Thus, the input matching circuit 93 has a circuit
configuration which is similar to that of a low-pass filter. Further, in
this input matching circuit 93 of the low-pass type, the parameters such
as the inductance of the coil 96 and the capacitance of the capacitor 97
are set in such a manner that a matching is performed correspondingly to
the center frequency f2 of the transmission input signal A2.
Incidentally, a coupling capacitor 98 is provided between the input
terminal 82 and the input matching circuit 92 of the low-pass type.
The high-frequency amplifier 91 constructed as above described, namely,
this embodiment has advantages or effects that are nearly the same as
those of the high-frequency amplifier 81, namely, the fourth embodiment.
Incidentally, because both of the input matching circuits 92 and 93 of
this embodiment are of the low-pass filter type, the circuit
characteristic of the input matching circuit 92 and that of the input
matching circuit 93 depend upon each other. Thus, each of the parameters
of the coil 94 and the capacitor 95 and each of the parameters of the coil
96 and the capacitor 97 are set by being regulated in such a manner that
the matching corresponding to the transmission input signal A1 and the
matching corresponding to the transmission input signal A2 are
simultaneously performed.
Next, the case of application of yet another high-frequency amplifier
embodying the present invention, namely, a sixth embodiment of the present
invention to a high-frequency amplifier for amplifying a transmission
signal of a portable telephone of the common type will be cited as yet
another example, and will be described by referring to FIG. 9.
Characteristic aspects of this high-frequency amplifier 101 of the present
invention, namely, this embodiment reside in that an input matching
circuit 102 of the high-pass type, which is constituted by a matching
circuit of the high-pass filter type, is employed as a first input
matching circuit for performing a matching corresponding to the
transmission input signal A1, whose center frequency is f1 (namely, 902.5
MHz), and that an input matching circuit 103 of the high-pass type, which
is constituted by a matching circuit of the high-pass filter type, is
employed as a second output matching circuit for performing a matching
corresponding to the transmission input signal A2, whose center frequency
is f2 (namely, 1440 MHz).
Namely, the input matching circuit 102 of the high-pass type is constituted
by connecting a capacitor 104 and a coil 105 with each other in an
L-shaped configuration, similarly as the input matching circuit 78 of the
high-pass type in the case of the aforementioned third embodiment. Thus,
the output matching circuit 102 has a circuit configuration which is
similar to that of a high-pass filter. Further, in this input matching
circuit 102 of the high-pass type, the parameters such as the capacitance
of the capacitor 104 and the inductance of the coil 105 and are set-in
such a manner that a matching is performed correspondingly to the center
frequency f1 of the transmission input signal A1.
Moreover, the input matching circuit 103 of the high-pass type is
constituted by connecting a capacitor 106 and a coil 107 with each other
in an L-shaped configuration, similarly as the aforementioned input
matching circuit 102 of the high-pass type. Thus, the input matching
circuit 103 has a circuit configuration which is similar to that of a
high-pass filter. Further, in this input matching circuit 103 of the
high-pass type, the parameters such as the capacitance of the capacitor
106 and the inductance of the coil 107 are set in such a manner that a
matching is performed correspondingly to the center frequency f2 of the
transmission input signal A2.
The high-frequency amplifier 101 constructed as above described, namely,
the sixth embodiment has advantages or effects that are nearly the same as
those of the high-frequency amplifier 91, namely, the fifth embodiment.
Incidentally, in the case of the aforesaid first or second embodiment, the
input matching circuit 34 of the high-frequency amplifier 31 (61) is
constituted by a matching circuit of the low-pass filter type. However,
the present invention is not limited thereto. The input matching circuit
of the high-frequency amplifier 31 (61) may be constituted by a matching
circuit of the high-pass filter type.
Further, in the case of the aforesaid second embodiment, the output
matching circuits 62 and 63 of the high-frequency amplifier 61 is
constituted by a matching circuit of the low-pass filter type. However,
the present invention is not limited thereto. Each of the output matching
circuits of the high-frequency amplifier 61 may be constituted by a
matching circuit of the high-pass filter type.
Moreover, in the case of the high-frequency amplifier 81 of the fourth
embodiment, the input matching circuit 83 of the high-pass type is
connected to the input terminal 82. Further, the input matching circuit 86
of the low-pass type is connected to the output side or terminal of the
input matching circuit 83 of the high-pass type. However, if the input
matching circuit 83 of the high-pass type and the input matching circuit
86 of the low-pass type are replaced with each other and are then
connected to this high-frequency amplifier, such a new high-frequency
amplifier is substantially the same as the high-frequency amplifier of the
fourth embodiment. Namely, the input matching circuit 86 of the low-pass
type may be connected to the input terminal 82. Moreover, the input
matching circuit 83 of the high-pass type may be connected to the output
side of the input matching circuit 86 of the low-pass type.
Furthermore, in the descriptions of the aforementioned embodiments, the
cases, in which the high-frequency amplifiers 31, 61, 71, 81, 91 and 101
are provided in the portable telephones of the common type, have been
cited as examples and described. However, the present invention is not
limited thereto. The high-frequency amplifiers of the present invention
can be applied to and used as high-frequency amplifiers for amplifying the
two kinds of high-frequency signals, whose frequencies are different from
each other.
Besides, in the foregoing descriptions of the embodiments, the
high-frequency amplifiers 31, 61, 71, 81, 91 and 101 have been described
as power amplifiers. The present invention is not limited thereto. The
high-frequency amplifiers may be used as small signal amplifiers.
Although the preferred embodiments of the present invention have been
described above, it should be understood that the present invention is not
limited thereto and that other modifications will be apparent to those
skilled in the art without departing from the spirit of the invention.
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